Metformin is a medication used for the management of Type 2 diabetes and is available with a prescription. It belongs to a class of medications called the biguanides, and is the only biguanide available in the United States. It is the preferred drug for patients newly diagnosed with Type 2 diabetes. It may be used in combination with other anti-diabetics, such as insulin or glyburide. Metformin comes as an extended release tablet and as an immediate release tablet; a physician can determine which tablet the patient needs as well as the dose.
Action in the Body
Metformin works to reduce the blood sugar levels in several ways. It directly stimulates the breakdown of glucose, or sugar, in the body and increasing the release of glucose out of the body. According to "Pharmacotherapy: A Pathophysiologic Approach," it also decreases the production of glucose in the liver and slows down the absorption of glucose from the stomach and intestines.
Vitamin B-12
Vitamin B-12 is a water-soluble vitamin found in animal products, including fish, poultry, meat, milk, eggs and milk products. Vitamin B-12 is necessary for proper red blood cell formation, nerve function and production of new cells.
Metformin's Effects
Metformin reduces the amount of vitamin B-12 absorbed, especially when used for a long period of time. According to the "Drug Information Handbook," about 7 percent of patients may develop decreased vitamin B-12 levels and are more at risk of developing a deficiency. The reason metformin impairs the ability to absorb vitamin B-12 efficiently is unknown.
Deficiency
Vitamin B-12 is measured by a blood test to determine how much is present in the plasma, which the yellow liquid portion of the blood. The Office of Dietary Supplements explains that values between 170 and 250 pg/mL for adults indicate a vitamin B-12 deficiency. However, this measurement might not accurately represent the amount of vitamin B-12 in the body. Homocysteine, a chemical found in plasma, may be measured also; an elevated level may also indicate vitamin B-12 deficiency.
Symptoms
Symptoms of vitamin B-12 deficiency include anemia, fatigue, constipation, weakness and weight loss. The patient may also experience numbness or tingling in the hands and feet. The Office of Dietary Supplements states that additional symptoms include imbalance, confusion, depression, memory impairment and dementia. If the patient develops any of these symptoms, he should contact a physician right away. These symptoms are not exclusive to vitamin B-12 deficiency, and the physician can evaluate the patient properly.
Monitoring and Supplementation
Patients on metformin should be screened annually for vitamin B-12 levels to determine if levels are within normal range, says "Basic and Clinical Pharmacology." The physician may wish to measure homocysteine levels as well. The physician can determine whether a patient is deficient and requires vitamin B-12 injections. The patient should never use vitamin B-12 unless a physician says it is necessary.
References
- "Pharmacotherapy: A Pathophysiologic Approach"; Joseph T. Dipiro, Robert L. Talbert, et al.; 2008
- "Drug Information Handbook"; Charles F. Lacy, Lora L. Armstrong, et al.; 2009
- Office of Dietary Supplements: Vitamin B-12
- "Basic and Clinical Pharmacology"; Bertram G. Katzung; 2007
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